Perforated non-woven fabrics of polymer material are well known in the art. Representative examples include U.S. Pat. Nos. 5,714,107 to Levy et al., 4,615,671 to Bernal and 3,864,198 to Jackson. In each of these prior art patents the polymer material is slit or cut and then subjected to stretching to provide a honeycomb web or open cell structure.
Unfortunately, the stretching of the material to open the honeycomb or cellular structure leads to the tearing of a significant number of the fiber-to-fiber bonds thereby reducing the strength and integrity of the resulting material. Further, the tearing of so many bonds also increases the friability of the material. Thus, erection of the honeycomb web or cellular material in accordance with prior art methods leads to two significant detrimental results.
Co-pending U.S. patent application Ser. Nos. 10/889,442 filed on 12 Jul. 2004 and 11/024,081 filed on 28 Dec. 2004 (owned by the assignee of the present invention) disclose a honeycomb web precursor and a method of producing a honeycomb web of polymer material wherein the precursor is erected by folding rather than stretching. Accordingly, the resulting product has improved fiber-to-fiber bond integrity and exhibits reduced friability when compared to prior art cellular structures.
The present invention relates to a further improvement that utilizes a novel slit pattern to produce an expanded panel with substantially triangular shaped openings that is suited for a number of different applications.